#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
#define x first
#define y second
typedef pair<int,int> pii;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> void chkmax(T &x,T y){x<y?x=y:T();}
template <typename T> void chkmin(T &x,T y){x>y?x=y:T();}
template <typename T> void readint(T &x)
{
    x=0;int f=1;char c;
    for(c=getchar();!isdigit(c);c=getchar())if(c=='-')f=-1;
    for(;isdigit(c);c=getchar())x=x*10+c-'0';
    x*=f;
}
/*const int MOD=;
inline int dmy(int x){return x>=MOD?x-MOD:x;}
inline void inc(int &x,int y){x=dmy(x+y);}
int qmi(int x,int y)
{
    int ans=1;
    for(;y;y>>=1,x=1ll*x*x%MOD)
        if(y&1)ans=1ll*ans*x%MOD;
    return ans;
}*/ 

int n,m;
void solve()
{
    int ans=1<<30,x,y;
    readint(n),readint(m);
    for(int i=1;i<=n;++i)
    {
        readint(x),readint(y);
        chkmin(ans,y*((m-1)/x+1));
    }
    printf("%d\n",ans);
}

int main()
{
    #ifdef LOCAL
    freopen("code.in","r",stdin);
//    freopen("code.out","w",stdout);
    #endif
    int T;
    readint(T);
    while(T--)solve();
    return 0;
}